The above image shows my "boat anchor" receiver, a Drake R4A of 1965 vintage hooked up to my 2001 vintage K2. The R4A is being used as an outboard receiver with a buffer amplifier fitted internally within the K2, together with an external mute unit. Here is a link to the full article in Adobe Acrobat format (400 KB file size).

Having the access to some quite sophisticated test equipment, I thought I would share some measurements I've made on my Elecraft transceivers. The serial numbers are K1 serial 1154 and K2 serial 1892. The K2 uses an "A" series motherboard partly modified to the "B" version. I have two "band" boards for the K1, one is configured for 80 and 40 metres, the other is a four band board built for 40/30/20/15 metres.
Later versions of the K2, i.e. those you could buy today from Elecraft, include the PLL and "A to B" modifications.

The following table shows the image figures obtained after modifying the band pass filters, while they are not as good as an up conversion transceiver, they are adequate for most users. Beware the 2nd receiver input option (K160RX) gives much worse image figures on some bands as the TX low pass filter isn't used via that input. Measurements done with Marconi 2018.

The "A to B" modifications made no difference to the 21 MHz figures.

Another part of the "A to B" modifications involve changes to the PLL and BFO in an effort to improve frequency drift, while the modification does improve it, the figures aren't impressive. There is a later modification that replaces the PLL crystal and adds a thermistor board in place of RP3. Details of my measurements of drift and frequency error are shown below.

Frequency error varies from band to band on a K2 as it doesn't use a single master oscillator. The errors measured after 30 minutes warm up with my K2 plus thermistor board are as follows:

K1 drift figures have been revised. My original figures were quite bad with a drift in excess of 200 Hz/hour. I changed the ceramic capacitor at C2 for a polystyrene one, this improved the temperature stability slightly but I was never satisfied with the result... The K1 seems to always drift more than I was comfortable with. After a little investigation among various articles on VFO building, I concluded that polystyrene capacitors were not good news in a VFO and bought another 68 pF "NP0" capacitor locally. Much to my amazement, the drift figure halved and is now just under 100 Hz per hour after 5 minutes warm up. The K1 display appears sluggish and doesn't give an accurate indication of slow frequency drift, I suspect this is because the software stops the last digit flickering between two digits. My measurements were made using an external counter.

Power output levels from both the K1 and K2 are quite near the indicated figures.
Power level in Watts has been calculated from dBm levels and rounded to nearest tenth of a Watt.

Sensitivity measurements , made with Marconi 2018 and DVM. These were measured after the A to B mods were done on the K2. The reason for poor sensitivity on 15m and 10m has been found to be the band pass filters are now narrower than original (due to the A to B mods to improve image rejection), this seems to have resulted in the filters drifting off frequency when warm. I will re-align and post the new figures when I have a spare hour. The "new" sensitivity on 10m is 0.16uV without pre-amp and 0.1uV with. I suspect the poor performance of the pre-amp in the figures below has to do with amplifying more noise than signal due to the filters needing re-alignment. There was an issue with early trimmers fitted to the first K1 four band boards, these were found to be temperature sensitive and were replaced with blue coloured trimmers. The same issue may have now arisen with the narrower filters in the K2.

The other significant modification (official Elecraft 2nd filter modification) flattens the response of the 2nd filter and improves the SSB receive audio significantly, the following plots show the "before" and "after" results:

I used to run a Microwave Modules MMT144/28 transverter with my K2. If you would like details of the interface, attenuator and interconnections, download this Adobe Acrobat file (92 KB).

Those who struggle to tune their antenna with the KAT1 (internal auto ATU in the K1) may like to try the following modification in Adobe Acrobat(147 KB)